In another southern Egyptian city, security officials said a Coptic man stabbed his wife for converting to Islam and for trying to see their son afterward.

Both incidents highlight the rise in sectarian tension in Egypt over the past two years, brought on in part by deterioration in police powers since the ouster of longtime President Hosni Mubarak in 2011.

The country's Christian minority has long complained of discrimination. Some ultraconservative Muslim groups, allegedly emboldened by Islamist electoral gains since Mubarak's fall, have lately been accused of inciting violence against the Christians, who make up around 10 percent of the country's 90 million people.

Officials say 24-year-old teacher Dimiana Abdel-Nour will be held for another 15 days in a southern village near the famed city of Luxor where she taught history and geography. The defendant, who has denied the charges, went on hunger strike earlier this week and was sent to a local hospital.

Amnesty International called on Egyptian authorities to release the school teacher. Some of her students say she showed contempt while talking about Islam in class last month and insulted the Prophet Muhammad.

Amnesty's Hassiba Hadj Sahraoui said it was "outrageous that a teacher finds herself behind bars for teaching a class," adding that if Abdel-Nour had made a "professional mistake or deviated from the curriculum, an internal review would have sufficed."

Often in Egypt, tensions between Muslims and Christian are sparked by inter-religious love affairs or conversions.

In the stabbing case, police officials said Romany Amir stabbed his wife Saturday in Assiut while she was trying to visit her son at school. The wife had converted to Islam four months ago and had been separated from her husband since then. He is under arrest.

The officials spoke anonymously because they were not authorized to speak to media.